Chapter 3 Laboratory Experiences

 

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  1. Use a ruler to measure the dimensions of the sole of one of your shoes in centimeters. Being as accurate as possible, calculate an estimate of the surface area of the sole. (If a planimeter is available, use it to more accurately assess surface area by tracing around the perimeter of the sole.) Knowing your own body weight, calculate the amount of pressure exerted over the sole of one shoe. How much change in pressure would result if your body weight changed by 22 N (5 lb)?

    2. Surface area: 

    Body weight: 

    Pressure: 

    Pressure with 22N (5 lb) change in body weight:

  2. Place a large container filled 3y4 full of water on a scale and record its weight. To assess the volume of an object of interest, completely submerge the object in the container, holding it just below the surface of the water. Record the change in weight on the scale. Remove the object from the container. Carefully pour water from the container into a measuring cup until the container weighs its original weight less the change in weight recorded. The volume of water in the measuring cup is the volume of the submerged object. (Be sure to use correct units when recording your measured values.)

    3. Weight of container of water:
     

    Change in weight with object submerged: 

    Volume of object: 

  3. Secure one end of a pencil by firmly clamping it in a vise. Grip the other end of the pencil with an adjustable wrench and slowly apply a bending load to the pencil until it begins to break. Observe the nature of the break.

    4. On which side of the pencil did the break begin? 

    Is the pencil stronger in resisting compression or tension? 

    Repeat the exercise using another pencil and applying a torsional (twisting) load. What does the nature of the initial break indicate about the distribution of shear stress within the pencil?

  4. Experiment with pushing open a door by applying force with one finger. Apply force at distances of 10 cm, 20 cm, 30 cm, and 40 cm from the hinges. Write a brief paragraph explaining at which force application distance it is easiest/hardest to open the door.

  5. Stand on a bathroom scale and perform a vertical jump as a partner carefully observes the pattern of change in weight registered on the scale. Repeat the jump several times, as needed for your partner to determine the pattern. Trade positions and observe the pattern of weight change as your partner performs a jump. In consultation with your partner, sketch a graph of the change in exerted force (vertical axis) across time (horizontal axis) during the performance of a vertical jump.

    6. What does the area under the curve represent?